U.S. Pat. No. 6,511,257 describes a reusable mat system for the construction of load bearing surfaces, such as temporary roadways and equipment support surfaces, over unstable or unsubstantial terrain, comprising durable, interlocking individual mats which can be quickly and easily installed in a single application, and which can thereafter be easily removed and stored until needed again. The individual mats interlock on all sides to form stable and continuous load bearing surfaces, and exhibit favorable traction characteristics.
U.S. Pat. No. 6,652,183 describes a road mat that includes a body having a first end, a second end, a first face and a second face. A first coupling is positioned at the first end has an outwardly extending portion extending outwardly from the first end adjacent to the second face, an angled portion extending from a remote end of the outwardly extending portion toward but not past the first face, and an inwardly extending retaining lip extending from a remote end of the angled portion back toward the first end. A second coupling is positioned at the second end is similarly configured with an outwardly extending portion extending outwardly from the second end adjacent to the first face, an angled portion and an inwardly extending retaining lip. The retaining lip of the second coupling engages the retaining lip of the first coupling preventing separation.
U.S. Pat. No. 7,413,374 describes a portable overlapping secured mat system with uniformly sized plastic mats joined together to form structural support surface for use by persons or equipment. The mats' edges have recessed upper and lower lips with finger projections extending from the upper lips sized to fit into holes of adjacent mats' lower lips securing the mats together when the front edge of the finger projections are moved into a recesses of the back wall of the hole.